from datetime import datetime, timedelta

def days_since(start_date_str):
    # 将输入的字符串转换为日期对象
    start_date = datetime.strptime(start_date_str, '%Y-%m-%d')
    # 获取当前日期
    today = datetime.today()
    # 计算两个日期之间的差值
    delta = today - start_date
    return delta.days, start_date + timedelta(days=1000)

# 示例用法
start_date_input = input("请输入开始日期 (格式: YYYY-MM-DD): ")
days, thousandth_day = days_since(start_date_input)
print(f"从 {start_date_input} 到今天共 {days} 天")
print(f"从 {start_date_input} 的第 1000 天是 {thousandth_day.strftime('%Y-%m-%d')}")